text: // Copyright Louis Dionne 2013-2017
  // Distributed under the Boost Software License, Version 1.0.
  // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
  
  #include <boost/hana/assert.hpp>
  #include <boost/hana/chain.hpp>
  #include <boost/hana/equal.hpp>
  #include <boost/hana/optional.hpp>
  
  #include <laws/base.hpp>
  namespace hana = boost::hana;
  using hana::test::ct_eq;
  
  
  int main() {
      auto f = [](auto x) {
          return hana::just(hana::test::_injection<0>{}(x));
      };
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::chain(hana::just(ct_eq<3>{}), f),
          f(ct_eq<3>{})
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::chain(hana::nothing, f),
          hana::nothing
      ));
  
      // test with operators
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::just(ct_eq<3>{}) | f,
          f(ct_eq<3>{})
      ));
  
      BOOST_HANA_CONSTANT_CHECK(hana::equal(
          hana::nothing | f,
          hana::nothing
      ));
  }
  